Hi @lowolelow
I can't find a service manual for the camera (Canon aren't that friendly) but you may wish to consider the following [https://www.ebay.com/sch/i.html?_from=R40&_nkw=canon+a3100+IS+&_sacat=0&_sop=15|option] of getting a faulty camera and using it as a donor for parts, especially the CCD sensor which seems the most likely suspect in your camera.
This [https://wiki.recessim.com/view/Canon_PowerShot_A3100_IS|link] may also be useful as it shows the different internal components used in the camera